Vacuum distillation process



May 17, 1938- K. c. D. HICKMAN 2,117,803

VACUUM DI STILLATION PROCESS Filed Dec. 4, 1936 7 3 F05. a. Z2

x 27 Z n i 37 FREE Kenneth Cllfiickman INVENTOR. BY

ATTORNEYS Patented May 17, 19 38 VACUUM DISTHILATION PROCESS Kenneth G.n. Hickman, Rochester, N. Y., a. signor to Eastman Kodak Company,Rochester, N. Y., a corporation of New Jersey Application December 4,1936, Serial No. 114,226

In Great Britain July 8, 1936 1 7. Claims. (01. 202-44) This inventionrelates to improvements in vacuum distillation and particularly in thevacuum distillation of thermally labile materials such as vitamins.

In carrying out the high vacuum distillation of marine animal oils toseparate vitamin containing distillates it has been found that lossesdue to thermal decomposition and/or oxidation were substantial andincreased greatly with elevation of. temperature. This action was'ioundtobe especially troublesome when recovering the high boiling forms ofvitamins A and D which distill over a temperature range of about 1BO-260 C. At these temperatures the vitamins can be heated for only ashort period of time, vitamin D being especially heat labile and shouldnot usually be heated for a period greatly exceeding a few seconds ifsubstantial decomposition is to be avoided. The distillation procedureheretofore employed, namely flowing the oil by gravity over a heatedsurface in a thin film, necessitated such prolonged heating thatdecomposition could not be avoided. While decomposition of the lowerboiling forms of vitamins A and D, which distill at about 118 and 144 C.respectively, is not as great, it is sufflcient to reduce the economy ofthe process.

- This invention has for its object to overcome the deficiencies of theabove described processes. Another object is to provide a processwhereby thermally unstable materials can be vacuum distilled withoutsubstantial loss due to thermal destruction. A further object is toprovide a high vacuum distillation process whereby fat soluble vitaminscan be distilled without material loss 5. due to thermal decompositionor oxidation. A still further object is to provide a process of shortpath vacuum distillation whereby rapid vaporizer-- tion takes place andonly a short heating period is necessary. Other objects will appearherein- 40 after.

These objects'are accomplished by subjecting the material containing theheat labile compound to be distilled, such as a vitamin containing oilto the direct heating action of the vapors of a compound having a lowervapor pressure than the substance to be recovered as distillate. In itspreferred form the invention involves disposing In carrying out myinvention a body of the vthe still as illustrated and is housed-inbearing l4 and gas tight bearing l5. Disc shaped plates .connects tovacuum pumps (not shown) which heating vapor is produced in andmaintained under a vacuum. This can be conveniently done by passing theliquid to be vaporized over a heated surface inside the evacuatedchamber. The material to be distilled is then directly contacted withthese vapors preferably while it is in a form such that its surface areais greatly increased. This condition can be obtained by spraying it intothe heated vapors to form minute droplets which are immediately heatedby the vapors, or the materlalflcan be thrown into the vapors'in theform of a continuous or broken sheet of extreme thinness. Other means ofobtaining fine subdivision can be used such as converting the materialinto a fog or mist in which the particles are of such small dimensionsthat they are hardly affected by gravitational force.

When the material to be distilled is introduced into the vapors in thisdivided state it is apparent that each small particle .or droplet willalmost 20 immediately be heated to the temperature of the heatingvapors. For this reason vaporization takes place instantaneously and asquick condensation follows, the heating period required for thedistillation is enormously reduced as compared to prior known processes.

In the accompanying drawing I have illustrated sectional elevations oftwo forms of apparatus in which my invention can be conveniently carriedout.

Referring to Fig. 1 reference numeral I designates a cylindricaldistillation chamber provided with a conduit 2 in the base thereof andthe walls of which are provided with annular gutters 3 and 4 which areprovided with withdrawal conduits 5 and 6. The top 1 is fixed to thestill chamber in gas tight manner by flanges 8 and 9 as shown. Part Islopes inwardly to form a dome which terminates in a cylindrical portionl0. Conduit Ii communicates with cylindrical portion in and serve toevacuate the still chamber. A shaft l2 provided with a driving pulley l3extends into 20 and 2| are mounted upon shaft l2, disc 2| being s0located that it is on the same horizontal plane as the center of gutter3 Conduits 22 and 23 terminate just above the central surfaces of discs20 and 2| respectively and serve to convey liquids onto the uppersurfaces thereof. The lower portion of chamber l is provided with alayer of insulating material 24 in which is disposed an electricalheating unit 25 terminating a substantially horizontal line A-A. Due torein'leads 26 and 21 through which the heating current is circulated.

Referring to Fig. 2, numeral 35 designates a cylindrical lower sectionand 36 the upper por-.

' and at the other end to conduit 40 which connects with high vacuumpumps (not shown). A shaft 4| extends the length of the still chamberand is housed at the lower end in bearing 42 and 'at the upper end ingas tight bearing 43. The

shaft is provided with a disc 44 and a driving pulley 45. A conduit 46terminates near the upper surface of disc 44 and is provided with aninternal heating coil 41 which is heated by electrical currentcirculated through leads 46 and 46. The entire still chamberis coveredwith a heat insulating jacket 56 in which is disposed an electricalheating unit which terminates in leads 52 and 53. A conduit 54communicates with the lowest portion of the base of section 35. Conduit40 is flared outwardly to form an annular channel 55, the lower portionof which communicates with conduit 56.

In operating the apparatus of Fig. 1 the system is evacuated throughconduit i l, the walls of i are heated by unit 25 and the heating fluidto be vaporized and which may be preheated is introduced through conduit22. Shaft I2 is caused to rotate at a high speed-and fluid dropping on'disc 20, is thrown off as a sheet or spray by centrifugal force and isheated by contact with the heated walls. When the temperature isproperly regulated for the particular heating substance and vacuum used,vaporization of the heating substance takes place and the vapors willsubstantially remain in the lower portion of the chamber forming a vaporline or point of condensation at evaporation on the walls and in thebase, the introduction of fluid through a conduit 22 may be intermittentor relatively slow. When the body of heating vapors is thus established,material to be distilled which is preferably degassed and preheated isintroduced through conduit 23 at a regulated rate. The liquid falling onplate 2| isthrown on as a very thin film, spray or fog,

' depending on the speed of rotation. and the material is thus'broughtinto intimate contact with the heating vapors. Volatile constituents arevaporized and nonvolatile constituents with condensed heating fluid fallor flow to the base. The vapors thus generated travel up into contactwith the 'cool walls of I where they are condensed and flow down intogutter 4 and may be withdrat'vn'through conduit 6. Accumulatedundistilledresidue is withdrawn continuously or intermittently throughconduit 2. ".When shaft I2 is rotated at slower speeds a thin sheet ordroplets having a horizontal direction of travel are thrown into gutter3 and may be withdrawn through conduit 5. Since the material thuscollected has travelled through the hot vapors for an appreciabledistance they will have lost all of the desired volatiles or only partthereof depending on the distance, temperature, material distilled,speed of rotation, etc. These can be varied to give complete or partialdistillation. In case the latter is desired, complete recovery can beeffected either by a second or plurality of passages through the samestill or through a number of stills in series.

In operation, employing the apparatus of Fig. 2,

condense on the spray flung from the disc.

the still is evacuated through conduit 40 and the heating liquid isintroduced either through con duit 46 or 54. Unit 5| is heated to theappropriate temperature and a body of heating vapors thus established inthe still. then put in operation and the mixture to be distilled isintroduced through conduit 46. The preheated mixture fallsontorotating-disc 44 and is dispersed in the heating vapors in the samemanner as described in connection with Fig. 1. Vaporized moleculestravel through conduit 36 and are condensed in conduit 46." Thecondensate.

desirable to preheat the distilland before it is sprayed into thevapors. It is best to preheat to as high a temperature as possiblewithout initiating thermal decomposition and thenquickly spray theheated distilland into the heating vapors where the distillation atdestructive temperatures is completed in a very short period of time.The preheater illustrated in Fig. 2 could be used with advantage in theapparatus of Fig. 1. Obviously other widely different forms ofpreheaters could be employed. It is possible that slight decompositionwill take place during the preheating step and it is therefore desirableto preheat as rapidly as possible.

For optimum results the rate of admission of distilland, and thetemperature of the heating vapors are so regulated that the heatingvapors vapors of heating fluid are then replaced by vapors of distillatewhich pass upwards into the speeds of rotation of between about 500 to6000 R. P. M. are usually most satisfactory, but higher speeds up toabout 25,000 R. P. M. give finer subdivision and are therefore desirablein certain cases; Also the heating vapors can be generated outside ofthe still and introduced into the distilling chamber in any desiredmanner.

' As pointed out above, the heating fluid should have a lower vaporpressure than the substance to be recovered as distillate. If the vaporpressure approaches that of the distillate the vapor line will be closeto the condenser and contami nation of the condensate by the heatingfluid will result. This is not objectionable in many cases and suchprocedure may be advantageous to follow in distilling many materials.Whereno contamination is desired, or only slight contamination can betolerated it is best to employ a heatpressure than that of the desireddistillate.

Heating unit 41 is The heating fluid employed may be any organiccompound which has the requisite vapor pressure and which can bevaporized without substantial decomposition under the conditions'oftemperature and pressure employed. It should not be a compound whichwill react with the distillate unless such reaction is desired.Materials such as hydrocarbons, especially of high boiling point,alcohols, esters such as glycerides for instance natural animal andvegetableoils, trimyristin, tripall'nitin, tri-pelargonin, trilaurin,triolein, di/

this way the material distilled is made to furnish its own vapor ofheating fluid.

The conditions of temperature and pressure employed in the process of myinvention will obviously vary with the particular material beingdistilled. Temperatures between 100 and 350 C. are most generally used,and those between about 100 and 300 C. and especially 100-250 0.

when vitamins are recovered from natural oils. Since the heating periodis very brief, temperatures considerably in excess of normaldecomposition points can be used. Pressures of less than 20 mm. aredesirable and when recovering vitamins it is desirable to operate atbelow 1 mm.

and preferably below .1 mm. such as for instance at between about .01and .0001 mm.

The process of my invention is applicable toof low vapor pressure.Vitamins can be recovered from animal and vegetable oils andconcentrates thereof such as cod-liver, halibut, tuna, salmon, sardine,menhaden, dog-fish, herring etc., body and liver oils. Sterols,hormones, sterol glucosides of the digitalis type, unsaturatedglycerides etc. are examples of other materials which can be distilledwith ease by proceeding in accordance with my invention.

It is preferredto employ distillation apparatus in which the evaporatingzone and condensing surfaces are separated by free unrestricted space.The distance between the two can vary greatly, but it is desirable tohave them separated by a distance such that contamination of the'condensing surface by heating vapors is slight. Since very rapidvaporization takes place pressures higher than those used in moleculardistillation can be used. Distances of separation may be molecular i. e.at less than the mean free path, but it is preferable to use greaterdistances in order to decrease contamination. Distillate can bewithdrawn through large admittance side tubes and condensed at adistance as illustrated in Fig. 2. This construction is useful when itis desired to decrease heat losses due to radiation.

When distilling oxidizable material or when using low pressures SUL-) asbelow .1 mm., it is best. to degas the distilland before it isintroduced into the still. This can be accomplished by subjecting themixture to high vacuum while warming slightly if desired. A preferredmethod of this general nature is disclosed in my co -pending application#48,691 filed November 6, 1935.

What I claim is:

1. The process of distilling an organic mixture which is fluid at thetemperature of distillation, which comprises spraying the mixture in afinely subdivided state into a localized body of hot vapors maintainedunder a pressure of below about .1 mm. and condensing molecules whichare vaporized by contact with the hot vapors upon a condensing surfacewhich is not in contact with the localized body of hot vapors, the bodyof hot vapors being derived from a substance which has a substantiallylower vapor pressure than the distillate at the operating conditions.

2. The process of distilling an organic mixture which is liquid at thetemperature of distillation which comprises spraying the mixture in afinely subdivided state into a localized body of hot vapors which ismaintained under a high vacuum and condensing molecules which arevaporized by contact with the hot vapors upon a condensing surface whichis not in contact with the localized body of hot vapors, the body of hotvapors being derived from a substance which has a lower vapor pressurethan the condensate at the operating conditions.

3. The process of distilling an organic'mixture which is fluid at thetemperature of distillation which comprises spraying the mixture in aflnely subdivided state into a localized body of hot vapors which ismaintained under a high vacuum and condensing molecules which arevaporized by contact with the hot vapors upon a condensing surface whichis not in contact with the localized body of hot vapors, the body of hotvapors being derived from a glyceride which has 4 1a substantially lowervapor pressure than the distillate at the operating conditions.

4. The process of distilling an organic mixture which is fluid at thetemperature of distillation and which contains a thermally unstableconstituent to be removed as a distillate which comprises spraying'themixture in a finely subdivided state into a localized body of hot vaporswhich is maintained under a pressure of below about .1 mm. andcondensing molecules which are vaporized by contact with the hot vaporsupon a condensing surface which is not in con-' tact with the localizedbody of hot vapors, the body of hot vapors being derived from asubstance which has a lower vapor pressure than the distillate at theoperating conditions.

5. The process of distilling an oil' containing a vitamin whichcomprises spraying the oil in a.

finely subdivided state into a localized body of hot vapors maintainedundera pressure of below about .1 mm. and condensing vitamin moleculeswhich are vaporized by contact with the hot vapors upon a condensingsurface which is not in contact with the localized body of hot vapors,the body of hot vapors being derived from a substance which has a lowervapor pressure than the vitamin distillate at the operating conditions.

6. The process of distilling a flsh oilcontain ing a vitamin whichcomprises spraying the oil vapors, the body of hot vapors being derivedfrom a substance which has a lower vapor pressure than the vitamindistillate at the operating conditions.

7, The process of distilling a fish oil contain- 7 ing a vitamin whichcomprises spraying the oil in a finely subdivided state into a localizedbody of vapor maintained at a temperature of about 100 to 300 C. andunder a pressure of below about .1 mm., and condensing vitamin moleculeswhich are vaporized by contact with the hot vapors upon a condensingsurface which is not mm c. n. HICKMAN.

